The application generally relates to variable speed drives. The application relates more specifically to controlling the ratio of voltage to frequency output by a variable speed drive or variable frequency drive.
In a chiller system or other heating, ventilation, air conditioning or refrigeration (HVAC&R) system where the compressor is coupled with a variable frequency drive (VFD) or variable speed drive (VSD), the compressor motor is typically sized to operate at a particular voltage-to-frequency (V/f) ratio and a particular load point. Because the compressor in the actual system can operate during a variety of conditions, the motor is typically not operating at peak efficiency.
Therefore, what is needed is a variable speed drive or variable frequency drive that can vary the ratio of voltage to frequency to compensate for varying load conditions.